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Commit 30070984 authored by Daniel Mack's avatar Daniel Mack Committed by David S. Miller
Browse files

cgroup: add support for eBPF programs 



This patch adds two sets of eBPF program pointers to struct cgroup.
One for such that are directly pinned to a cgroup, and one for such
that are effective for it.

To illustrate the logic behind that, assume the following example
cgroup hierarchy.

  A - B - C
        \ D - E

If only B has a program attached, it will be effective for B, C, D
and E. If D then attaches a program itself, that will be effective for
both D and E, and the program in B will only affect B and C. Only one
program of a given type is effective for a cgroup.

Attaching and detaching programs will be done through the bpf(2)
syscall. For now, ingress and egress inet socket filtering are the
only supported use-cases.

Signed-off-by: default avatarDaniel Mack <daniel@zonque.org>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0e33661d

include/linux/bpf-cgroup.h

0 → 100644
+79 −0
Original line number Diff line number Diff line 
#ifndef _BPF_CGROUP_H

#define _BPF_CGROUP_H



#include <linux/bpf.h>

#include <linux/jump_label.h>

#include <uapi/linux/bpf.h>



struct sock;

struct cgroup;

struct sk_buff;



#ifdef CONFIG_CGROUP_BPF



extern struct static_key_false cgroup_bpf_enabled_key;

#define cgroup_bpf_enabled static_branch_unlikely(&cgroup_bpf_enabled_key)



struct cgroup_bpf {

	/*

	 * Store two sets of bpf_prog pointers, one for programs that are

	 * pinned directly to this cgroup, and one for those that are effective

	 * when this cgroup is accessed.

	 */

	struct bpf_prog *prog[MAX_BPF_ATTACH_TYPE];

	struct bpf_prog *effective[MAX_BPF_ATTACH_TYPE];

};



void cgroup_bpf_put(struct cgroup *cgrp);

void cgroup_bpf_inherit(struct cgroup *cgrp, struct cgroup *parent);



void __cgroup_bpf_update(struct cgroup *cgrp,

			 struct cgroup *parent,

			 struct bpf_prog *prog,

			 enum bpf_attach_type type);



/* Wrapper for __cgroup_bpf_update() protected by cgroup_mutex */

void cgroup_bpf_update(struct cgroup *cgrp,

		       struct bpf_prog *prog,

		       enum bpf_attach_type type);



int __cgroup_bpf_run_filter(struct sock *sk,

			    struct sk_buff *skb,

			    enum bpf_attach_type type);



/* Wrappers for __cgroup_bpf_run_filter() guarded by cgroup_bpf_enabled. */

#define BPF_CGROUP_RUN_PROG_INET_INGRESS(sk,skb)			\

({									\

	int __ret = 0;							\

	if (cgroup_bpf_enabled)						\

		__ret = __cgroup_bpf_run_filter(sk, skb,		\

						BPF_CGROUP_INET_INGRESS); \

									\

	__ret;								\

})



#define BPF_CGROUP_RUN_PROG_INET_EGRESS(sk,skb)				\

({									\

	int __ret = 0;							\

	if (cgroup_bpf_enabled && sk && sk == skb->sk) {		\

		typeof(sk) __sk = sk_to_full_sk(sk);			\

		if (sk_fullsock(__sk))					\

			__ret = __cgroup_bpf_run_filter(__sk, skb,	\

						BPF_CGROUP_INET_EGRESS); \

	}								\

	__ret;								\

})



#else



struct cgroup_bpf {};

static inline void cgroup_bpf_put(struct cgroup *cgrp) {}

static inline void cgroup_bpf_inherit(struct cgroup *cgrp,

				      struct cgroup *parent) {}



#define BPF_CGROUP_RUN_PROG_INET_INGRESS(sk,skb) ({ 0; })

#define BPF_CGROUP_RUN_PROG_INET_EGRESS(sk,skb) ({ 0; })



#endif /* CONFIG_CGROUP_BPF */



#endif /* _BPF_CGROUP_H */

include/linux/cgroup-defs.h

+4 −0
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
#include <linux/percpu-refcount.h>

#include <linux/percpu-rwsem.h>

#include <linux/workqueue.h>

#include <linux/bpf-cgroup.h>



#ifdef CONFIG_CGROUPS
@@ -300,6 +301,9 @@ struct cgroup { 
	/* used to schedule release agent */

	struct work_struct release_agent_work;



	/* used to store eBPF programs */

	struct cgroup_bpf bpf;



	/* ids of the ancestors at each level including self */

	int ancestor_ids[];

};

init/Kconfig

+12 −0
Original line number Diff line number Diff line
@@ -1154,6 +1154,18 @@ config CGROUP_PERF 


	  Say N if unsure.



config CGROUP_BPF

	bool "Support for eBPF programs attached to cgroups"

	depends on BPF_SYSCALL && SOCK_CGROUP_DATA

	help

	  Allow attaching eBPF programs to a cgroup using the bpf(2)

	  syscall command BPF_PROG_ATTACH.



	  In which context these programs are accessed depends on the type

	  of attachment. For instance, programs that are attached using

	  BPF_CGROUP_INET_INGRESS will be executed on the ingress path of

	  inet sockets.



config CGROUP_DEBUG

	bool "Example controller"

	default n

kernel/bpf/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -5,3 +5,4 @@ obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list 
ifeq ($(CONFIG_PERF_EVENTS),y)

obj-$(CONFIG_BPF_SYSCALL) += stackmap.o

endif

obj-$(CONFIG_CGROUP_BPF) += cgroup.o

kernel/bpf/cgroup.c

0 → 100644
+167 −0
Original line number Diff line number Diff line 
/*

 * Functions to manage eBPF programs attached to cgroups

 *

 * Copyright (c) 2016 Daniel Mack

 *

 * This file is subject to the terms and conditions of version 2 of the GNU

 * General Public License.  See the file COPYING in the main directory of the

 * Linux distribution for more details.

 */



#include <linux/kernel.h>

#include <linux/atomic.h>

#include <linux/cgroup.h>

#include <linux/slab.h>

#include <linux/bpf.h>

#include <linux/bpf-cgroup.h>

#include <net/sock.h>



DEFINE_STATIC_KEY_FALSE(cgroup_bpf_enabled_key);

EXPORT_SYMBOL(cgroup_bpf_enabled_key);



/**

 * cgroup_bpf_put() - put references of all bpf programs

 * @cgrp: the cgroup to modify

 */

void cgroup_bpf_put(struct cgroup *cgrp)

{

	unsigned int type;



	for (type = 0; type < ARRAY_SIZE(cgrp->bpf.prog); type++) {

		struct bpf_prog *prog = cgrp->bpf.prog[type];



		if (prog) {

			bpf_prog_put(prog);

			static_branch_dec(&cgroup_bpf_enabled_key);

		}

	}

}



/**

 * cgroup_bpf_inherit() - inherit effective programs from parent

 * @cgrp: the cgroup to modify

 * @parent: the parent to inherit from

 */

void cgroup_bpf_inherit(struct cgroup *cgrp, struct cgroup *parent)

{

	unsigned int type;



	for (type = 0; type < ARRAY_SIZE(cgrp->bpf.effective); type++) {

		struct bpf_prog *e;



		e = rcu_dereference_protected(parent->bpf.effective[type],

					      lockdep_is_held(&cgroup_mutex));

		rcu_assign_pointer(cgrp->bpf.effective[type], e);

	}

}



/**

 * __cgroup_bpf_update() - Update the pinned program of a cgroup, and

 *                         propagate the change to descendants

 * @cgrp: The cgroup which descendants to traverse

 * @parent: The parent of @cgrp, or %NULL if @cgrp is the root

 * @prog: A new program to pin

 * @type: Type of pinning operation (ingress/egress)

 *

 * Each cgroup has a set of two pointers for bpf programs; one for eBPF

 * programs it owns, and which is effective for execution.

 *

 * If @prog is %NULL, this function attaches a new program to the cgroup and

 * releases the one that is currently attached, if any. @prog is then made

 * the effective program of type @type in that cgroup.

 *

 * If @prog is %NULL, the currently attached program of type @type is released,

 * and the effective program of the parent cgroup (if any) is inherited to

 * @cgrp.

 *

 * Then, the descendants of @cgrp are walked and the effective program for

 * each of them is set to the effective program of @cgrp unless the

 * descendant has its own program attached, in which case the subbranch is

 * skipped. This ensures that delegated subcgroups with own programs are left

 * untouched.

 *

 * Must be called with cgroup_mutex held.

 */

void __cgroup_bpf_update(struct cgroup *cgrp,

			 struct cgroup *parent,

			 struct bpf_prog *prog,

			 enum bpf_attach_type type)

{

	struct bpf_prog *old_prog, *effective;

	struct cgroup_subsys_state *pos;



	old_prog = xchg(cgrp->bpf.prog + type, prog);



	effective = (!prog && parent) ?

		rcu_dereference_protected(parent->bpf.effective[type],

					  lockdep_is_held(&cgroup_mutex)) :

		prog;



	css_for_each_descendant_pre(pos, &cgrp->self) {

		struct cgroup *desc = container_of(pos, struct cgroup, self);



		/* skip the subtree if the descendant has its own program */

		if (desc->bpf.prog[type] && desc != cgrp)

			pos = css_rightmost_descendant(pos);

		else

			rcu_assign_pointer(desc->bpf.effective[type],

					   effective);

	}



	if (prog)

		static_branch_inc(&cgroup_bpf_enabled_key);



	if (old_prog) {

		bpf_prog_put(old_prog);

		static_branch_dec(&cgroup_bpf_enabled_key);

	}

}



/**

 * __cgroup_bpf_run_filter() - Run a program for packet filtering

 * @sk: The socken sending or receiving traffic

 * @skb: The skb that is being sent or received

 * @type: The type of program to be exectuted

 *

 * If no socket is passed, or the socket is not of type INET or INET6,

 * this function does nothing and returns 0.

 *

 * The program type passed in via @type must be suitable for network

 * filtering. No further check is performed to assert that.

 *

 * This function will return %-EPERM if any if an attached program was found

 * and if it returned != 1 during execution. In all other cases, 0 is returned.

 */

int __cgroup_bpf_run_filter(struct sock *sk,

			    struct sk_buff *skb,

			    enum bpf_attach_type type)

{

	struct bpf_prog *prog;

	struct cgroup *cgrp;

	int ret = 0;



	if (!sk || !sk_fullsock(sk))

		return 0;



	if (sk->sk_family != AF_INET &&

	    sk->sk_family != AF_INET6)

		return 0;



	cgrp = sock_cgroup_ptr(&sk->sk_cgrp_data);



	rcu_read_lock();



	prog = rcu_dereference(cgrp->bpf.effective[type]);

	if (prog) {

		unsigned int offset = skb->data - skb_network_header(skb);



		__skb_push(skb, offset);

		ret = bpf_prog_run_save_cb(prog, skb) == 1 ? 0 : -EPERM;

		__skb_pull(skb, offset);

	}



	rcu_read_unlock();



	return ret;

}

EXPORT_SYMBOL(__cgroup_bpf_run_filter);